The invention concerns a monitoring arrangement for a high-frequency surgery device. The monitoring arrangement has a control electrode applied on a body, far removed from an active electrode, the control electrode reading during treatment, a high-frequency voltage existing on the body surface relative to the potential of a neutral electrode. The monitoring arrangement also has a monitoring circuit including a voltage comparator controlled by the control electrode. The voltage comparator compares a voltage depending on body surface voltage with a pre-established reference voltage and, upon exceeding the reference voltage, activates a signal transmitter and/or a relay switching-off the high-frequency surgery device.
With a known monitoring apparatus of this type (German patent DE-PS No. 33 06 402), the voltage read by the control electrode is introduced initially to a squaring stage, after which the squared voltage is introduced to an integrating stage, and the squared and integrated voltage is compared in a comparator circuit with a reference voltage. However, this known monitoring arrangement is based upon the premise that the total electrical energy, which is obtained on the one hand from the product of the electrical field strength and the current density, and, on the other hand, from the period of operation, represents a measure for the danger of burning.
It has been shown that even with the same amount of introduced total electrical energy, and even with regular and orderly contact of the neutral electrode to the body surface, the effective heat development at the most loaded body location beneath the neutral electrode is different for individual patients.
The invention is therefore based upon the object of providing a monitoring arrangement for a high-frequency surgery device of the above-described type which, in spite of individual differences in heat development for particular patients, eliminates with certainty any danger of burning.